Plasma processing apparatus and a plasma processing method

ABSTRACT

In an oxide film etching, a plasma having a suitable ratio CF 3 , CF 2 , CF, F is necessary and there is a problem in which in accordance with a temperature fluctuation of an etching chamber an etching characteristic is fluctuated. Using UHF type ECR plasma etching apparatus having a low electron temperature, a suitable dissociation can be obtained, and forming a temperature adjustment range of a side wall at from 10° C. and 120° C. a stable etching characteristic can be obtained. Since the oxide film etching using the low electron temperature and high density plasma can be obtained, an etching result having a superior characteristic can be obtained, and also since a side wall temperature adjustment range is low, an apparatus structure and a heat resistant performance countermeasure can be performed easily.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a plasma processing apparatusand a plasma processing method and in particularly to an apparatus foretching an insulation film such as a silicon oxide film of a wafer usinga plasma and relates to a plasma etching apparatus and a plasma etchingmethod having a plasma generation source which can be corresponded to aminute practicing of an etching pattern and further enable formaintaining a stable etching characteristic during a long period.

[0002] Among conventional plasma processing apparatuses, an oxide filmplasma etching apparatus is exemplified and techniques and problems ofthis apparatus are shown. As the conventional plasma source of an oxidefilm use etching apparatus, a type which is used most widely is a narrowelectrode type high frequency plasma generation apparatus which iscomprised of a pair of opposing electrodes.

[0003] The systems of the narrow electrode type high frequency plasmageneration apparatus have known that there is a system in which a highfrequency having from 13.56 MHZ to a several 10 MHZ degree is applied toone electrode and to another electrode by mounting a wafer a highfrequency bias having about 1 MHZ to the wafer is applied separately andthere is another system in which a high frequency is applied to a pairof electrodes.

[0004] In this plasma source system etching apparatus, since a distancebetween the electrodes is narrow from 20 mm to 30 mm, it is called as anarrow electrode type plasma source and a parallel flat plate typeplasma source.

[0005] Further, in the narrow electrode type plasma source it isdifficult to generate a plasma generation at a region where a pressureis low, however by an addition of a function of a magnetic fieldapplication etc., an apparatus in which a lowering of a dischargepressure is improved is used.

[0006] Further, in addition to the above stated apparatus, plasmaetching apparatuses have known, these apparatuses are one plasma etchingapparatus having an induction type plasma source in which an inductioncoil is used and another plasma etching apparatus having a microwaveplasma etching microwave is introduced.

[0007] In these induction type etching source and the microwave typeplasma sources, it is possible to generate and maintain the plasma undera low pressure and further since a plasma density is high, the abovestated plasma source is called as a low pressure and a high densityplasma source.

[0008] In a silicon oxide film etching, as an etching gas, one mixturegas in which to argon (Ar) a gas including carbon (C) and fluorine (F)such as C₄F₈ and a gas including hydrogen (H) such as CHF₃ are mixed isused and further another mixture gas in which oxygen (O₂) and a carbonmonoxide CO, and hydrogen (H₂) etc. are added the above stated onemixture gas is used.

[0009] These gases are dissociated by the plasma and dissolved to CF₃,CF₂, CF, and F. An amount and a ratio of this gas molecule species giveslargely an influence on an etching characteristic of the silicon oxidefilm (hereinafter, it is called merely as an “oxide film”).

[0010] In particularly, in the case of the high density plasma source,since an electron temperature in the plasma is high, the plasmadissociation is progressed, and the plasma has many fluorine gasmolecule kind F. Further, an ionization is progressed and it has afeature in which a ratio of a neuter gas molecule species (radicals) islow.

[0011] With these reasons, in the oxide film etching according to thehigh electron temperature and the high density plasma, since an amountof CFx (CF₃, CF₂, CF) which adheres to a silicon surface being afoundation of the oxide film is lowered, there are problems in which anetching speed of silicon (Si) is large and a selection ratio is small.

[0012] As means for solving the above stated problems, a method forincreasing CFx radical amount in the plasma has known, namely atemperature of a wall face of an etching chamber is risen to about 200°C., and a deposition film which is adhered to the wall face is tried todischarge, and an adhesion to the deposition film to the wall face ofthe etching chamber is restrained.

[0013] As a result, in the apparatus in which the high density plasma isused, to obtain the selection ratio a high temperature performance ofthe wall face of the etching chamber becomes indispensable.

[0014] An oxide film etching apparatus described in Japanese applicationpatent laid-open publication No. Hei 7-183283 is an example where a wallface of an etching chamber is formed with the high temperatureperformance.

[0015] As a countermeasure for obtaining the high selection ratio inaddition to the above technique, it has known a method in which anelectron temperature in the plasma is lowered and a plasma dissociationis restrained. In concretely, a plasma application is carried outintermittently and this method is called as a pulse plasma method.

[0016] As another one example for obtaining the high selection ratio,there is a method in which materials for consuming the fluorine (F) areinstalled in an etching chamber in advance. In Japanese applicationpatent laid-open publication No. Hei 9-283494, the above stated methodis shown, a side wall of an etching chamber is constituted by silicon(Si), a heating means of the side wall and a bias application means areprovided, and the fluorine (F) in the plasma is consumed.

[0017] In the oxide film etching in which the narrow electrode typeplasma is used, in correspondence with the fine practicing in which adevice pattern size moves to less than 0.25 μm, to a portion to besubjected the etching it is necessary to make extremely small ascattering of an ion incident angle.

[0018] Since the scattering of the ion incident angle causes anabnormality of an etching shape and an ion amount for reaching to abottom of a deep hole is decreased, there are problems in which alowering of an etching speed is caused and a stop of the etching iscaused.

[0019] The scattering of the ion incident angle is caused by the causein which an incident angle distribution has a spread angle because theions collide with the radicals in the plasma. To solve the above statedproblems, it is effective to decrease the collision of the ion with theradicals, in concretely it is necessary to lower the pressure.

[0020] As a result, in the narrow electrode type plasma generationapparatus in which the plasma discharge is difficult to carry out underthe low pressure, even under the low pressure enable for generate theplasma, there is devised that the frequency of the plasma generationsource is made to the high frequency and the magnetic field is applied.

[0021] Further, in the narrow electrode type plasma source in which thedistance between the electrodes is narrow, in a case where the lowpressurization is devised, since an average free stroke of the gasmolecule becomes long, the collision frequency of the gas moleculestogether with is decreased, in place of this the collision between thegas molecules and the electrode becomes dominate.

[0022] This is not a preferable condition as the etching apparatus inwhich according to the collision of the gas molecules in the plasma itis necessary to control the maintenance and the reaction of the plasma,and as a result so as to correspond the low pressurization it isnecessary to form large the electrode interval.

[0023] When the electrode interval is formed wide, a rate of an area ofthe side wall which occupied with a surface area in the etching chamberbecomes large. The surface of the etching chamber indicates one which issubjected to the plasma and the surface does not a surface of a topplate (a ceiling), a surface of a floor, and a surface of the electrode(the wafer).

[0024] Until now, in the narrow electrode type plasma source, viewingfrom an aspect of the plasma and a wafer, since the side wall area isnarrow, the deposition and the gas discharge in the side wall do notalmost give the influence to the etching characteristic, however in thenarrow electrode type plasma apparatus in which the low pressurizationis devised, it is necessary to take a new countermeasure.

[0025] Further, to correspond to a large diameter sizing of the wafer,it is necessary to uniform a gas pressure distribution in a wafer faceand a reaction product distribution and for this purpose it is necessaryto form wide the electrode interval, and an importance of the area ratioof the side wall becomes high more and more.

[0026] The influence of the affects of the react product which isadhered to the side wall to the etching characteristic is shown inabove, however when the etching is continued extending over during along period, a change of the influence degree becomes a problem.

[0027] For example, by carrying out repeatedly the etching thetemperature of the side wall is risen gradually. When the temperature ofthe side wall is risen, the characteristic of the adhesion andadsorption of the reaction product to the side wall is changed, as aresult the etching characteristic is fluctuated.

[0028] Further, in a case where the amount of the deposition film to theside wall accompanying with the etching is increased gradually, inaccordance with the dependence to the amount of the deposition film itis possible to change the desorption and adsorption characteristic ofthe reaction product at the side wall surface.

[0029] A phenomenon in which the etching characteristic receives theinfluences according to the time lapse change stated in above is knownin particularly in the case of the oxide film etching. As a result, thetemperature adjustment of the side wall in the oxide film etchingapparatus is an important problem.

[0030] In particularly, in the high electron temperature and highdensity plasma source, it is compelled to establish the side walltemperature high. In the above stated high side wall temperature, eventhe side wall temperature is fluctuated a little, the adsorption anddesorption characteristic of the deposition film is changed largely.

[0031] With these reasons, it is necessary to restrain the side walltemperature fluctuation in a small range, and the high accuracytemperature adjustment such as 200° C.±2° C. is carried out.

[0032] As stated in above, in any of the plasma sources, to satisfy therequirement of the oxide film etching, namely the obtaining the highetching speed by attaining the high selection ratio, the low microloading, the passing -through of the deep hole, it remains the problemto be solved.

[0033] The important problem in the oxide film etching apparatus is thatthe dissociation of the gas molecule according to the plasma is formedas a most suitable condition in the etching of the oxide film. Tocorrespond to this, it has proposed a new plasma generation sourcehaving a high density plasma under low electron temperature.

[0034] For example, as described in Japanese application patentlaid-open publication No. Hei 8-300039, there is UHF type ECR apparatushaving a plasma excitation frequency of UHF band from 300 MHZ to 1 GHz.An electron temperature of the plasma which is excited by the frequencyband having the above stated range is low from 0.25 eV to 1 eV and theplasma dissociation of C₄F₈ has a level for suitable to the oxide filmetching. Further, since it is ECR (Electron Cyclotron Resonance) system,even under the low pressure it is possible to generate the high densityplasma.

[0035] As stated in above, for the correspondence to the fine practicingand the wafer large diameter sizing, it is necessary to make theelectron temperature low and to restrain the excess dissociation of theetching gas and further to make the plasma density high.

[0036] Further, it is necessary to uniform the plasma density, the gaspressure and the reaction product distribution on the wafer, and as aresult it is necessary to provide an apparatus in which an oxide filmetching characteristic is not changed extending over during a longperiod.

SUMMARY OF THE INVENTION

[0037] An object of the present invention to provide a plasma processingapparatus and a plasma processing method wherein, using UHF type ECRplasma etching apparatus enable for generate a high density plasma undera low electron temperature necessary for an oxide film etching etc., afluctuation of an etching characteristic can be restrained smallextending over during a long period.

[0038] Another object of the present invention to provide a plasmaprocessing apparatus and a plasma processing method wherein, using UHFtype ECR plasma etching apparatus enable for generate a high densityplasma under a low electron temperature necessary for an oxide filmetching etc., a stop of an etching is not generated and also a stableoperation or a stable work can be carried out.

[0039] The characteristic according to the present invention is that ina plasma processing apparatus or in a plasma processing method using avacuum processing chamber, a sample table for mounting a sample which isprocessed in said vacuum processing chamber, and a plasma generationmeans, the plasma processing apparatus, wherein when a plasma processingis carried out by generating a plasma according to an introduction of agas which contains at least carbon and fluorine, and by generating a gasspecies which contains carbon and fluorine according to a plasmadissociation, said plasma generation means is a plasma generation meansin which a degree of said plasma dissociation is a middle degree andsaid gas species containing the carbon and the fluorine is generatedfully in the plasma, and a temperature of a region which forms a sidewall of said vacuum processing chamber is controlled to have a range of10° C. to 120° C.

[0040] In UHF type ECR plasma etching apparatus has a UHF band microwaveradiation antenna at an opposite position to a wafer, and from a gassupply portion provided on an antenna portion an etching gas issupplied. The UHF band microwave is radiated directly to a plasma fromthe antenna and is radiated in the plasma through a dielectric bodywhich is provided at a periphery of the antenna.

[0041] In an electrode for mounting the wafer (a wafer mount electrodeor a lower electrode), an etching position and a wafer delivery positionare positioned at separate positions and an electrode ascent and descentfunction is provided. A distance (it is called as an “electrode betweendistance”) between the wafer mount wafer and the antenna or the gassupply plate is established from 50 mm to 100 mm taking into theconsideration about such a re-association of a reaction product.

[0042] According to the plasma processing apparatus, a side walltemperature at a periphery of the electrode is temperature adjusted witha range of 10° C. to 120° C., preferably a range of 30° C. to 50° C. Theside wall temperature is fluctuated, a gas species is discharged from adeposition film of the side wall and this gives an influence of anetching characteristic.

[0043] In the present invention, to restrain the above stated influence,a temperature control accuracy of the side wall is controlled at ±5° C.Since the side wall temperature is low, even the temperature of the sidewall is fluctuated be at 5° C. degree, since the fluctuation of adischarge gas amount which is discharged from the side wall, theinfluence on the etching characteristic can be neglected.

[0044] Further, since the plasma source is UHF type ECR system, a plasmadissociation is a middle degree and CFx species exists fully to a levelnecessary for the oxide film etching, since a shortage of CFx speciesand an excess F which becomes the problems in the high density plasmasource can be solved and to heighten the selection ratio it isunnecessary to heighten the side wall temperature.

[0045] Herein, when the dissociation exceeds over F or C becomes richand when the dissociation is short F, CF₂, CF₃, etc become the shortage,accordingly it is desirable to have the plasma dissociation with themiddle degree. Further, since the side wall temperature is controlledthe low temperature, even the side wall temperature control accuracy is±5° C., the fluctuation of the etching characteristic can be restrainedat a long period.

BRIEF DESCRIPTION OF DRAWINGS

[0046]FIG. 1 is a schematic view showing an etching apparatus of aplasma processing apparatus and a plasma processing method of oneembodiment according to the present invention;

[0047]FIG. 2 is a view showing a size relationship of various kinds ofplasma sources of a plasma processing apparatus and a plasma processingmethod of one embodiment according to the present invention;

[0048]FIG. 3 is a view showing a characteristic of a gas discharge froma deposition film of a plasma sources of a plasma processing apparatusand a plasma processing method of one embodiment according to thepresent invention;

[0049]FIG. 4 is a view showing an influence of a side wall temperaturewhich gives an influence to a time lapse change of a plasma sources of aplasma processing apparatus and a plasma processing method of oneembodiment according to the present invention;

[0050]FIG. 5 is a view showing an etching speed change in a case where atemperature adjustment of a side wall is not performed according to theprior art; and

[0051]FIG. 6 is a view showing an etching speed change in a case where atemperature adjustment of a side wall is performed according to thepresent invention.

DESCRIPTION OF THE INVENTION

[0052] Hereinafter, a plasma processing apparatus and a plasmaprocessing method of one embodiment according to the present inventionwill be explained.

[0053]FIG. 1 is an example of UHF type ECR plasma etching apparatus. Ata peripheral portion of an etching chamber 1 (a vacuum processingchamber) which is a vacuum vessel, a coil 2 is installed, this coil 2generates an electron cyclotron resonance (ECR) use field.

[0054] An etching use gas is supplied from a gas supply pipe 3 and isintroduced to from a gas supply plate 4 to the etching chamber 1. Thegas supply plate 4 is comprised of a plate of a silicon form or a glassform carbon in which about 100 number fine holes having a diameter offrom 0.4 mm to 0.5 mm degree are provided.

[0055] At an upper portion of the gas supply plate 4, a disc formantenna 5 is provided and this antenna 5 radiates a microwave having UHFband. The microwave to the antenna 5 is supplied from a power supply 6through an induction shaft 7.

[0056] When the microwave is radiated from a periphery of the antenna 5,an oscillating electric field of an upper space of the antenna 5 isintroduced the etching chamber 1 through a dielectric body 8. Further,between the antenna 5 and an electrode 9 a volume combination electricfield is generated and this electric field becomes an effective plasmageneration source.

[0057] The frequency of the microwave is set to have a range of from 300MHZ to 1 GHz and has a band area in which an electron temperature of theplasma has a low temperature of from 0.25 eV to 1 eV.

[0058] In this embodiment according to the present invention, thefrequency band of a vicinity of 450 MHZ can be employed. Further, as thedielectric body 8, a quartz or an alumina can be employed. Further aheat resistant polymer having a small dielectric loss, such as apolyimide etc., can be employed.

[0059] The electrode for mounting a wafer (the wafer mount electrode ora sample table) 9 is provided on a lower portion of the gas supply plate4 and a wafer 10 being a sample is supported through an electrostaticadsorption. To draw into the ions in the plasma to the wafer 10, a highfrequency bias is applied to the wafer mount electrode 9 from a highfrequency power supply 11.

[0060] Further, the temperature control of an inner wall of the etchingchamber 1 being the vacuum processing chamber, which is an essentialfeature according to the present invention, is carried out at atemperature adjustment side wall 12 of the etching chamber 1.

[0061] To the temperature adjustment side wall 12, not shown in figure,a coolant medium which has temperature controlled is introduced and thetemperature adjustment side wall 12 is maintained at a constanttemperature. In this embodiment according to the present invention, theconstant temperature in the temperature adjustment side wall 12 is setto have 30° C.

[0062] The etching gas and the reaction product are deposited in theinner wall of the etching chamber 1 and also they are deposited at theperiphery and a downstream area of the wafer mount electrode 9 and thedeposition film become the generation origin of the foreign matters.

[0063] Accordingly, it is necessary to clean periodically the depositionfilm, however it is not always easy to remove the strongly adhereddeposition film. Herein, in this embodiment according to the presentinvention, the cleaning of the deposition film is carried out againusing an exclusive cleaning apparatus.

[0064] The transfer to a vacuum evacuation of the etching chamber 1,which has opened to the air, is important from an aspect of a shortageof a non-operation of the apparatus and further from an aspect of animprovement of a productivity.

[0065] Accordingly, it is desirable that the deposition film is tried tonot adhere a portion where the component exchange-over is not carriedout easily and that the component to which the deposition film hasadhered is tried to exchange over another prepared cleaning component.As a result, the air opening time in the etching chamber 1 can beshortened and a shortage of the vacuum evacuation after that can beimproved.

[0066] In this embodiment according to the present invention, not toadhere the deposition film to the downstream region of the etchingchamber 1, an deposition film use cover 13 is provided on the downstreamregion of the temperature adjustment side wall 12 of the etching chamber1.

[0067] To the cover 13, a vacuum evacuation use and a wafer delivery useopening portion is provided. Since the deposition film are recovered bythis cover 13, the adhesion of the deposition film in the downstreamregion of the temperature adjustment side wall 12 can be reduced.

[0068] A vacuum chamber 15 is connected directly to the etching chamber1 and a turbo molecular pump 14 having an evacuation speed of from 2000L/s to 3000 L/s is installed in the vacuum chamber 15. Further, notshown in figure, to an opening portion of the turbo molecular pump 14 avacuum evacuation speed adjustment use conductance valve 16 is installedand this evacuation speed adjustment use conductance valve 16 is usedfor separating the turbo molecular pump 14 during the air open time orthe evacuation speed adjustment use conductance valve 16 is used for notopening the air.

[0069] Next, an example of an oxide film etching using the plasmaprocessing apparatus of this embodiment according to the presentinvention will be explained.

[0070] To the etching chamber 1 which is vacuum evacuated at a highvacuum condition, not shown in figure, the wafer 10 is carried in from atransfer chamber by a transfer arm, and the wafer 10 is delivered on thewafer mount electrode 9.

[0071] The transfer arm is retarded and after a valve arranged betweenthe etching chamber 1 and a transfer chamber has closed, the wafer mountelectrode 9 is ascended and stopped a position where the etching iscarried out. In the case of this embodiment according to the presentinvention, a distance between the wafer 10 and the gas introductionplate 4 (an electrode between distance) is set to from 50 mm to 100 mm.

[0072] As the etching gas, a mixture gas comprised of Ar and C₄F₈, O₂ isused, and the respective flow amounts are 500 sccm, 10 sccm and 5 sccmare introduced. The pressure of the etching gas is 2 Pa. An output ofUHF microwave power supply is 1 kW, and an output of a bias power supply11 to the wafer 10 is 600 W.

[0073] The current is applied to the coil 2 and a resonance magneticfield having 0.016 T of UHF microwave having 450 MHZ is generatedbetween the gas supply plate 4 and the wafer mount electrode 9 (namelythe wafer 10). Next, the microwave power supply 6 is operated. Accordingto the electron cyclotron resonance, a strong plasma is generated in ECRarea having the resonance magnetic field strength of 0.016 T.

[0074] To improve the uniformity of the etching characteristic, it isnecessary to uniform an incident ion density on a surface of the wafer10 and when ECR is positioned as stated in above and a shape of ECR areais formed at a raised shape toward a side of the wafer 10, as a resultthe uniformity of the ion current density can be attained.

[0075] After a spark of the plasm, not shown in figure, from a directcurrent power supply which is connected directly in parallel with thehigh frequency power supply 11, a high voltage is applied to the wafermount electrode 9 and then the wafer 10 is electrostatic adsorbed to thewafer mount electrode 9.

[0076] At a rear face of the electrostatic adsorbed wafer 10, helium(He) gas is introduced, and the temperature adjustment of the wafer 10is carried out between a wafer mount face of the wafer mount electrode 9which has temperature controlled according to the coolant medium and thewafer 10 through the helium (He) gas.

[0077] Next, the high frequency power supply 11 is tried to be operated,the high frequency bias is applied to the wafer mount electrode 9.Accordingly, to the wafer 10 the ion is incident vertically from theplasm. In the oxide film etching, it is necessary to carry out the highenergy ion incident.

[0078] In this embodiment according to the present invention, a highfrequency bias voltage Vpp (the voltage between the maximum peak and theminimum peak) is made a value of from 1000 V to 2000 V. In accordancewith the impact due to the high energy ion, the temperature of the wafer10 is arisen.

[0079] In the oxide film etching, since the selection ratio is becomehigh in the higher temperature the etching characteristic has a superiorcharacteristic, the wafer temperature is adjusted to a value havingseveral 10° C.

[0080] However, since it is necessary to carry out the incident of thehigh energy ion, a heat input amount to the wafer 10 is large and thecoolant medium temperature of the wafer mount electrode 9 is set to avicinity of −20° C.

[0081] At the same time when the bias voltage is applied to the wafer10, the etching is started. The etching is finished under apredetermined etching time. Or, not shown in figure, by monitoring aplasma luminescence strength change of the reaction product and furtherjudging a finish point of the etching, an etching finish time isrequested and after a suitable over etching is performed, then theetching is finished.

[0082] The finish of the etching is a time when the application of thehigh frequency bias voltage is stopped. Simultaneously with this, thesupply of the etching gas is stopped.

[0083] However, it is necessary to provide a process in which theelectrostatically adsorbed wafer 10 is adsorbed from the wafer mountelectrode 9 and as an electric adsorption gas an Ar etc. is supplied. Bystopping the supply of the electrostatic adsorption voltage and after anelectric supply line is connected to an earth ground, maintaining thedischarge of the microwave an electric adsorption time having 10 secondsdegree is prepared. Accordingly, the electric charges on the wafer 10are adsorbed by the earth ground through the plasma, as a result thewafer 10 can be removed easily.

[0084] When the electric adsorption process is finished, the supply ofthe electric adsorption gas is stopped and also the supply of themicrowave is stopped. Further, the current supply to the coil 2 isstopped. Further, a height of the wafer mount electrode 9 is descendeduntil to the wafer delivery position.

[0085] After that for some time, the etching chamber 1 is vacuumevacuated until the high vacuum. At a time point of the high vacuumevacuation is completed, the valve between the etching chamber 1 and thetransfer chamber is opened and the transfer arm is inserted and then thewaver 10 is delivered and is carried out. In a case of an existence of anext etching process, a new wafer is carried in and the etching isperformed again according to the above stated procedures.

[0086] In above, the representative flow of the etching process wasexplained.

[0087] The electron temperature of UHF band microwave ECR plasma is arange of from 0.25 eV to 1 eV and the dissociation of C₄F₈ being theetching gas is not very progressed. The dissociation of C₄F₈ iscomplicated one, however the gas species which contributes the etchingis dissociated from CF₃ to CF₂, in next CF is generated, and finally Fis generated. As a result, the more the electron temperature is high,the more the plasma becomes one having F-rich plasma.

[0088] As stated in the prior art item, to ensure the selection ratio inthe oxide film etching, on the foundation silicon the deposition filmare adhered and it is necessary to restrain the etching according to thehigh energy incident. Namely, since the high energy ions are incident,when there are no deposition film, there a possibility in which theetching is progressed according to a physical sputter.

[0089] As a result, to progress the etching, it is necessary to supplythe high energy ions to the hole bottom, however to ensure the selectionratio, it is necessary to supply the radicals which form the depositionfilm. It is said that the radicals for forming the deposition film areCF₃ and CF₂.

[0090] In reversely, F radicals form SiF₄ etc. and the foundationsilicon is made to be etched. As a result, to perform the high selectionratio etching, it is necessary to make CF₂/F (CF₂-F ratio) large. In thecase of UHF band microwave ECR plasma, sine the electron temperature islow, the generation amount of F is small, the plasma having theplentiful CF₃, CF₂ and CF is formed.

[0091] Accordingly, as shown in the case of the high electrontemperature and the high density plasma, to supply CF₂ and CF₃ whichbecome insufficient by the excessive progress of the plasma dissociationof the plasma, it is unnecessary to heat the inner wall of the etchingchamber 1 more than 200° C.

[0092] As the necessary points for the fine practicing correspondenceetching, following points are stated, namely (1) under the low electrontemperature the plasma dissociation is restrained suitably and theplasma having the large CF₂/CF (CF₂-CF ratio) is generated, (2) thediscrepancy from 90° angle of the ion incident angle is restrained smalland a tapering formation of the etching shape, (3) even the etching isrepeated many times, the fluctuation of the etching characteristic issmall, etc.

[0093] In addition to the above an item relating to the etchingcharacteristics is an important development problem, however in thepresent specification such an item is not mentioned.

[0094] The above stated (1) item for the necessary points for the finepracticing correspondence etching is solved by the use of UHF bandmicrowave plasma etching apparatus according to the present invention.

[0095] As to the above stated (2) item for the necessary points for thefine practicing correspondence etching, a main cause is that the orbitis displaces according to the collision of the ions and the gasmolecular in the vapor phase and it is effective to lower the pressureto lessen the collision of the molecular.

[0096] Since UHF band microwave plasma etching apparatus according tothe present invention is used the electron cyclotron resonance, it ispossible to generate the plasma under the low pressure.

[0097] As to the above stated (3) item for the necessary points for thefine practicing correspondence etching, it is necessary to not fluctuatethe etching characteristic even the etching time numbers are repeated atseveral hundred order, namely it is necessary to restrain the time lapsechange.

[0098] A main cause of the time lapse change is the time fluctuation ofthe gas kinds which are discharged from the deposition film which adhereto the inner wall (the side wall, the ceiling, etc) and the componentsof the etching chamber 1. In concretely, the temperature fluctuation ofthe members to be subjected such as the side wall occupies the largecause.

[0099] As a countermeasure of the restraint of the time lapse change,basically the apparatus is formed to not fluctuate the desorption andadsorption phenomenon of the deposition film of the wall face accordingto the temperature control, however in accordance with the plasmageneration systems, the wall face area necessary to form as theapparatus differs.

[0100] The relationship between the etching chamber height and the sideface area is shown in FIG. 2. In the narrow electrode type plasma typeapparatus, the height of the etching chamber is low and also the area ofthe side wall face is narrow. On the other hand, in the high densityplasma type apparatus, the height of the etching chamber is high andalso the area of the side wall face is wide.

[0101] In UHF type ECR apparatus according to the present invention, theheight of the etching chamber (the electrode between distance) and thearea of the side wall are positioned intermediately and the apparatusoccupies the region which is suitable for the oxide film etching.

[0102] Namely, according to the present invention, the height of theetching chamber (the electrode between distance) and the area of theside wall has a middle value having 30 mm −100 mm of the narrowelectrode (about 30 mm) and the microwave ECR induction type (more than100 mm).

[0103] The height of the etching chamber, namely the electrode betweendistance, is a distance of from 50 mm to 100 mm, and the reactionproduct generated by the etching is re-dissociated and is re-incident tothe wafer 10.

[0104] With the above stated reasons, the etching characteristic of theoxide film receives an influence, however this is caused by making themost suitable performance to the influence degree such as there-dissociation and the incident of the reaction product etc. with theetching characteristic of the oxide film.

[0105] Namely, in this embodiment according to the present invention,the electrode between distance is formed according to a predetermineddistance which is determined by a relative relationship of a mean freestroke at a vicinity of the pressure of 2 Pa.

[0106] Since the electrode between distance is formed by the abovestated distance, the pressure distribution on the face of the wafer 10can be uniformed. In a case where the wafer diameter is formed largelyfrom 200 mm to 300 mm, the difference in pressure between the center andthe periphery of the wafer 10 can be small fully.

[0107] Further, since the conductance which depends on the electrodebetween distance is formed large, the high vacuum evacuation speed canbe obtained large fully, as a result the stay time of the etching gasand the reaction product can be shortened easily.

[0108] In a case where the area of the side wall is further wide, thereis a possibility in which the adhesion amount of the deposition filmbecomes large and then the influence degree to the etchingcharacteristic becomes large. In the apparatus for maintaining the highdensity plasma, according to the request of the plasma generationmethod, it is necessary to form the height of the etching chamber to arange from 100 mm to 200 mm.

[0109] Accordingly, the rate in which the area of the side wall occupieslargely in a whole area of the etching chamber is high and the influenceduring the fluctuation of the etching gas and the deposition of thereaction product in the side wall is large.

[0110] As the methods for restraining this influence, there are methodsin which the temperature fluctuation of the side wall is made to lessenor the side wall is heated under the high temperature to not adhere thedeposition film.

[0111] Further, as stated in the former portion, in the apparatus usingthe high density plasma source, since the electron temperature is high,the plasma having F-rich plasma is generated, to ensure the selectionratio it is necessary to reduce the gas species which adheres to theside wall or it is necessary to promote the gas discharge from thedeposition film, as a result it is necessary to make the side wall atthe high temperature.

[0112] With the above stated reasons, in the high electron temperatureand the high density plasma etching apparatus, the side wall is heatedat 200° C. degree and the temperature fluctuation is temperatureadjusted at a range of ±2° C.

[0113] However, it is difficult technically to heat the side wall at thehigh temperature more than 200° C. and also it is difficult technicallyto restrain with the high accuracy the temperature fluctuation such as±2° C. and further it invites the complicated structure in the apparatusand a problem in the reliability and the rise in cost. Further, the sidewall has the same meaning to the inner wall of the etching chamber, theside wall includes the top plate and other portions which contact to theplasma.

[0114] Further, in a portion is one where the deposition film adheres,when such a portion is not contacted directly, since this portion has apossibility for affecting the etching characteristic, in compliance ofthe apparatus, it is necessary to take fully into an attention.

[0115] Further, in the apparatus according to the present invention,since the side wall has from 50 mm to 100 mm degree, in the downstreamregion it can admit hardly the region where the deposition film isadhered.

[0116] As a result, as the oxide film plasma etching apparatus, it isdesirable to provide the apparatus in which the fluctuation of theetching characteristic is not generated even the temperature adjustmentaccuracy in the side wall temperature is mitigated.

[0117] In UHF type ECR plasma apparatus according to the presentinvention, it is unnecessary to heighten the side wall temperature toimprove the selection ratio. There is a merit in which the side walltemperature can be established according to the view point of therestraint of the time lapse change.

[0118]FIG. 3 shows the results in a case when the temperature of thedeposition film is changed 1° C., the gas discharge amounts from thedeposition film were measured.

[0119] It is understood that when the temperature of the deposition filmis high, there appear much gas amount which is discharged according tothe temperature fluctuation of 1° C. It is supposed that when the gaswhich corresponds to the flow amount of 0.01 sccm by the conversioncalculation of the flow amount of the etching gas, there is apossibility that the etching characteristic is given the influence andthe temperature adjustment range of the side wall temperature of thistime is shown in the right side in FIG. 3.

[0120] In a case of 200° C., when the side wall is not controlled at ±2°C., the fluctuation of the gas discharge amount becomes less than 0.01sccm. On the other hand, the side wall temperature is controlled lessthan 120° C., even the side wall temperature changes the change in thegas discharge amount is small.

[0121] Namely, it is understood that even the control accuracy of theside wall temperature is controlled with ±5° C. and ±10° C., the gasdischarge for giving the influence to the etching characteristic doesnot occur.

[0122] In the etching apparatus according to the present invention, theside wall temperature is established at a range of from 10° C. to 120°C. Preferably, it is controlled from the room temperature 20° C. to 50°C.

[0123] With this temperature range, since the etching chamber is notheated at the high temperature, there are merits that the dimension sizeof the apparatus is small and the materials of the vacuum sealing andthe material having the different thermal expansion coefficient can beused freely and the temperature control can be performed easily.

[0124] According to the present invention, it employs the system inwhich the coolant medium which is connected to the temperatureadjustment means is introduced to the side wall. By the employment ofthe above stated system, the temperature control performance can becarried out less than ±10° C.

[0125] Further, FIG. 3 shows the results in which the discharge amountsfrom the deposition film were searched. When the side wall temperaturebecomes the high temperature having more than 200° C., since theadhesion amounts of the deposition film themselves become small, in theapparatus having the high temperature control in which the depositionfilm are not adhered, as shown in an example in FIG. 3, the substantialgas discharge amounts become small.

[0126] The stability of the gas discharge amounts and the largeness ofthe fluctuation amounts into which the consideration of the adhesionamounts is taken are shown in FIG. 4.

[0127] In FIG. 4, the horizontal axis indicates the side walltemperature of the etching chamber and the horizontal axis indicates therelative largeness degree about the deposition film amount, theinfluence degree to the time lapse change and the gas discharge amount.

[0128] The gas discharge amount from the deposition film increasesabruptly from a vicinity which exceeds over 200° C. On the other hand,the adhesion amount of the deposition film to the side wall (thedeposition speed) reduces gradually in proportional to the hightemperature and decreases abruptly from the vicinity of 200° C.

[0129] The reason is why when the temperature exceeds over 200° C. andfurther when the temperature exceeds over more than 300° C. thedeposition film is not adhered to the side wall.

[0130] Accordingly, in the temperature range of the region 1 in FIG. 4,since the temperature is low the influence for referring to the etchingcharacteristic to the deposition film of the side wall is small.Further, in the region 3 in FIG. 4, since the temperature is high thegas discharge amount from the unit deposition film is much, however thedeposition film is hardly adhered, as a result the gas discharge amountis small, the influence to the etching characteristic is small.

[0131] However, in the region 2 in FIG. 4 which is the intermediatetemperature range between the both, the deposition film is comparativelylarge and the gas discharge amount is much, as a result the temperaturefluctuation of the side wall is given the influence largely to theetching characteristic.

[0132] Taking into the consideration from the above stated points, torestrain the time lapse change, the side wall temperature is set to theregion 1 or the region 3. The temperature range of the region 1 is lessthan 120° C. and in the region 3 the temperature range is more than 200°C. and in the region 2 the temperature range is from 120° C. to 200° C.

[0133] According to this embodiment according to the present invention,the side wall is established the temperature range of the region 1 inFIG. 4. Further, from the principle, the side wall temperature may beestablish to the low temperature, however taking into considerations thetemperature establishment is easily the temperature and the coolantmedium is not presented to the drew condensation, the lower limitationtemperature is set to 10° C.

[0134]FIG. 5 shows that in UHF type ECR plasma etching apparatus of theembodiment according to the present invention, the etching speedfluctuation is shown in a case of using the mixture gas containing Arand C₄F₈, the continuous etching is carried out.

[0135] In this time, since the temperature adjustment of the side wallis not carried out, the temperature fluctuation is risen accompanyingwith the discharge time of the plasma and is risen to 60° C. degree fromthe room temperature. The temperature fluctuation is ±20° C. degree. Theetching speed of the silicon nitride at the etching starting timebecomes high, it can be admitted the fluctuation of the etchingcharacteristic.

[0136] On the other hand, FIG. 6 shows the etching characteristic incase where the temperature adjustment of the side wall is carried out.

[0137] After the etching chamber is opened to the air and is carried outthe vacuum evacuation, without the performance of the covering about theinner portion of the etching chamber by the deposition film and also theprocess for presenting the regular state, regardless immediately theetching is started, the etching characteristic is stable from thestarting time of the etching, and the fluctuation after that is nothardly admitted. Further, the side wall temperature fluctuation at thistime is within ±5° C.

[0138] As understood from the above stated results, in UHF type ECRplasma etching apparatus, according to the performance of thetemperature adjustment of the side wall, the extremely stable etchingcharacteristic can be obtained.

[0139] Further, in this embodiment according to the present invention,it is explained on the assumption that UHF type ECR plasma etchingapparatus is used, however when the plasma source is suited for theetching of the oxide film, it is not limited to UHF type ECR plasmaetching apparatus.

[0140] Namely, when the electron temperature in the plasma is the lowelectron temperature having less than 1 eV and further the high densityplasma is used, for example, it can employ the apparatus using the pulseplasma source in which the application of the microwave is carried outintermittedly.

[0141] Further, it can employ the apparatus using the plasma source inwhich the induction type plasma except for the microwave is pulsedriven. When the side wall of the etching chamber of these plasmasources is established at a range of 10° C. to 120° C., it is possibleto obtain the superior oxide film etching characteristic and further itis possible to exhibit the stable characteristic during the long period.

[0142] Further, the temperature adjustment of the side wall isexemplified using the coolant medium, however it is not limited thecoolant medium, it can employ any one of the use of the compulsorycooling using the water cooling and the vapor cooling, the heater, thelamp heating using the infrared ray.

[0143] To summarize, the temperature range must be formed with the rangeof 10° C. to 120° C. With the above stated temperature range, even thetemperature adjustment range of the side wall is ±5° C. degree, thefully stable etching characteristic can be obtained.

[0144] According to the etching characteristic, even the temperatureadjustment range of the side wall is ±10° C. degree, the stable etchingcharacteristic can be obtained and further the temperature adjustmentcan be carried out extremely easily.

[0145] According to the present invention, since the superior oxide filmetching characteristic can be obtained and further the stablecharacteristic can be obtained during the long period, the followingmerits can be expected.

[0146] Namely, the yield can be improved and the throughput can beimproved. Further, since the temperature adjustment is established to atthe low temperature of from 10° C. to 120° C., the inconvenience inwhich the size of the etching chamber is made large by the thermalexpansion can be avoided.

[0147] For example, the line expansion coefficient of the aluminum alloywhich is largely in the etching chamber is 24×10⁻⁶K⁻¹, on the other handin the alumina and quartz the respective line expansion coefficients is6×10⁻⁶K⁻¹ and 0.41×10⁻⁶K⁻¹.

[0148] Since the line expansion coefficients differ so much, when theetching chamber is heated according to the plasm discharge or theetching chamber is temperature controlled compulsively at the hightemperature, the differences in the dimension sizes between thematerials become large and then it is necessary to devise structurallythe avoidance of the thermal expansion.

[0149] Further, the size change in the vacuum sealing portion gives theinfluence to the sealing characteristic, and further the heat resistantperformance of the elastomer being the seal material becomes a problem.

[0150] When the temperature becomes high to the level more than 150° C.,the possibility in which the life of the seal material presents shortbecomes high.

[0151] As stated in above, there cause the various problems in which theavoidance appears due to the high temperature and the heat resistantperformance is added structurally and the cost increases.

What is claimed is:
 1. In a plasma processing apparatus having a vacuumprocessing chamber, a sample table for mounting a sample which isprocessed in said vacuum processing chamber, and a plasma generationmeans, the plasma processing apparatus, wherein when a plasma processingis carried out by generating a plasma according to an introduction of agas which contains at least carbon and fluorine, and by generating a gasspecies which contains carbon and fluorine according to a plasmadissociation, said plasma generation means is a plasma generation meansin which a degree of said plasma dissociation is a middle degree andsaid gas species containing the carbon and the fluorine is generatedfully in the plasma, and a temperature of a region which forms a sidewall of said vacuum processing chamber is controlled to have a range of10° C. to 120° C.
 2. A plasma processing apparatus according to claim 1,wherein said plasma generation means is a plasma source in which anelectron temperature is a range of from 0.25 eV to 1 eV.
 3. A plasmaprocessing apparatus according to claim 1, wherein said plasmageneration means is an electron cyclotron resonance system in which amicrowave having a frequency of from 300 MHZ to 1 GHz.
 4. A plasmaprocessing apparatus according to claim 1, wherein in said plasmageneration means, a drive of a plasma exciting power supply is carriedout intermittedly.
 5. A plasma processing apparatus according to any oneof from claim 1 to claim 4, wherein as a means for adjusting atemperature of said vacuum wall, a temperature adjusted coolant mediumis used.
 6. In a plasma processing method using a vacuum processingchamber, a sample table for mounting a sample which is processed in saidvacuum processing chamber, and a plasma generation means, the plasmaprocessing method, wherein when a plasma processing is carried out bygenerating a plasma according to an introduction of a gas which containsat least carbon and fluorine and by generating a gas species whichcontains a carbon and fluorine according to a plasma dissociation, saidplasma generation means is a plasma generation means in which a degreeof said plasma dissociation is a middle degree and said gas speciescontaining the carbon and the fluorine is generated fully in the plasma,and a temperature of a region which forms a side wall of said vacuumprocessing chamber is controlled to have a range of 10° C. to 120° C. 7.A plasma processing method according to claim 6, wherein said plasmageneration means is a plasma source in which an electron temperature isa range of from 0.25 eV to 1 eV.
 8. A plasma processing method accordingto claim 6, wherein said plasma generation means is an electroncyclotron resonance system in which a microwave having a frequency offrom 300 MHZ to 1 GHz.
 9. A plasma processing method according to claim6, wherein in said plasma generation means, a drive of a plasma excitingpower supply is carried out intermittedly.
 10. A plasma processingapparatus according to any one of from claim 6 to claim 9, wherein as ameans for adjusting a temperature of said vacuum wall, a temperatureadjusted coolant medium is used.